Insulator



(NoModeL) G. T. LEE. INSULATOR.

No. 482,872. Patented Sept. 20, 18-92.

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UNITED STATES PATENT OFFICE.

CHARLES TENNANT LEE, OF BOSTON, MASSAOHUSE'I S, ASSIGNOR TO TH E JOHNSJRATT COMPANY, OF HARTFORD, (ONNE )TICU'I.

INSULATOR.

SPECIFICATION forming part of Letters Patent No. 482,872, datedSeptember 20, 1892.

' Applicationfiledli'cvemher 14,1891. Serial No. t1l,925.- iNoinudel.)

' To all whom, it may concern.-

Be it known that 1, CHARLES TENNANT LEE, a citizen of the United States,residing at 13oston, in the county of Suffolk and State of Mas- 5sachusetts, haveinvented certainnew and useful Improvements inInsulators, of which the following is a specification, reference beingtherein had to the accompanying drawings.

My invention has for its object to produce a durable and efficientinsulatorfor electrical purposes; and it consists of an insulatorcomprising an insnlation-blockeornposed of sheets of mica pressed andcompacted together, said block having a parallel-sided seat formed rthereon, and an outer case or shell, which incloses or partiallyincloses said block, the said case or shell having a clasping portion,which tightly compresses the seat formed on the edges of the sheet ofmica and which is held on the said sheet by frictional contact, all ashereinafter set forth, and the novel features of which are pointed outin the claims which are appended hereto.

It is not new, broadly, to construct an insulator having a stem or rodupon which are strung sheets of mica, and also having an outer casing,which 'isinsulated from the stem or rod by said sheets of mica; but suchinsulators, so far as known to me, have been difli- 3o cu1t,andconsequently expensive, to construct, and unless constructed with greatcare have been objectionable.

It is necessary to secure the parts of the insulator very firmlytogether, and to do this it p 5 has hitherto been usual to provide thecentral bolt or core with a head at its inner end, larger in size thanthe opening in the outer case,thus necessitating the making of the outercasein two parts and screwing them 0 or otherwise joining them together.The

making of thecase in two parts necessitates a joint, which isobjectionable for obvious reasons. An insulator made in accordance withmy invention is free from these objections.

In the accompanying drawingsI have shown two forms of my insulator.

Figure 1 represents a lengthwise central section of a handle which maybe used for any purpose for which an insulated handle is required. Fig.2 represents a lengthwise central section of one form of electricalinsulator which is known as strain-insulator and is used in the overheadconstruction of electrical railways.

My invention will be readily understood from the following description,in which reference is made to the accompanying drawings. The centralcore or metallic portion is shown at a, and consists of a rod of metalwhich is headed at one end to retain the mica in place andscrew-threaded at the other end, so that a retaining-nut 7L may besecured onto the rod to retain the mica in place at that end. Themica 1) consists of sheets, which are pro vided with a central aperture,through which the rod passes, and which are of a shape in the portion ofthe insulation-block which is inclosed and clasped by the case or shell(Z corresponding to the cross-sectional shape of the interior of thecase (Z. The sheets of mica. forming the said portion of theinsulationbloek should be cut as large or vt y little larger than thecross-section of the elasping portion of the shell or case and so thatthey cannot be slid into the case (Z when the case is cold. The exteriorof the said portion of the insulation-block forms a parallel-sided seat'of any desired outline in cross-section corresponding with that of theinterior of the clasping portion of the shell or case. The case d is ofmetal and may be of any convenient or desired exterior shape; but thatportion of its interior which is designed to come in contact with themica should be parallel-sided in the direct-ion of the length of thecase or shell. In applying the case or shell to the insulation-block themetallic case is heated, and when expanded by the heat the body or blockof insulating material is forced to place within it. The case is thenallowed to cool and shrink to its seat 011 the insulation. \Vhen shrunkto its place, it very tightly compresses its seat on theinsulation-block and is very firmly secured on said seat by itsfrictional contact therewith, and the insulator may be 5 subjected to agreat strain without breaking or separating the outer case from theinsulated core. As will be obvious, the mica sheets may be strung on roda, then compressed together, and then turned down to the size and zooshape desired. It will also be clear that the seat for the outer case onthe insulating ma- .ticity which is the quality of horn. Inpracteria1--that is, the part of the insulating ma terial which comes incontact with the outer case d-1naybe turned down or otherwise reduced,as shown'in the drawings, so that the finished insulator will have asmooth exterior, with no break or diiferenoe in the exterior diameterbetween the metal and the mica portions. the drawings.

In the strain-insulator, which is shown in Fig. 2, the constructionwhich 1 have de scribed is only varied-by the duplication of themetallic case d and by the formation of an annular flange f-i'n'the micaat a point about midway-between the metallic casings.

This annularfiange is for the purpose'o'f' allowing moisture to dropfreely from the insulator when it. is used out of doors. The

outer casing may be'varied in form, as de tice in fitting, together theparts it is necessary to apply-considerable pressurejin order to put theseat portion of the insulation-block within the receivingportion oftheshell or casing, even when the latter'is expanded by heat, the partsbeing-so proportioned as to secure such a iitas this implies. It isfound that, whereas beforethe insnlatinghloclr is 'lhis'is theconstruction shown in inserted into the shell or case the central coreor rodon which the mica sheets are strung admits of being withdrawn bythe exertion of a moderate degree of force, after the metal shell orcase-has been shrunk to its seat the sheets of mica have becomecompressed and shortened radially-that is, the radii of the disks are ofless 1engthand they are so.

forced in toward or on to the metal core or rod subjecting it to greatstrain, while, also, rod is found to be scored and out by the mica.

What I claim is 1. Ah insulator comprising an insulationblock composedof a series. of sheets of mica compressed and compacted together, thesaid block having a parallel-sided seat formed thereon, and a metallicshell .or casing inclosing or partially inclosing the said block,

lightly compressing the seat thereon, and

held on the seat by frictional contact, for the purposes andsubstantially as set forth.

2. An insulator comprising a core, a series of sheets of mica strung onsaid core and closely compressed and compacted together thereon, thesaid block having a parallel-sided seat formed thercon,and a metallicshell or casinginclosing or partially inclosin g the mica on said core,tightly compressing the seat thereon, and held on the seat by frictionalcontact, for the purposes and substantiall y as set forth.

In testimony whereof I aflix my signatu re in. presence of twowitnesses.

CHARLES TENNAN'I" LEE.

' \Vitnesses:

WM. A. Mltcnnon, Unas- F. RANDALL.

- that the latter cannot be Withdrawn unless by

